densely populated area

A super city

A Sparsely populated area

submerged or low-lying structures formed over time from the skeletons of small sea animals

economic system whereby people own and run businesses with limited government controls

businesses that provide services to customers rather than producing farm or industrial products

region of the Midwestern United States with flat land fertile soil

method of wheat farming in dry areas that conserves moisture by deep plowing

precipitation in which water carries large amounts of chemicals, especially sulfuric acid

referring to countries or people that rely on one another for certain trade items

overseas settlements that are tied to a parent country

a sudden radical change in government

a form of government in which people elect their own officials, including the leader of the country

a group of people who share a common culture, language or history

moving from place to place